I strongly suspect the identification page to be a
form-based page, that is, a page with a username and
password textfields embedded.
These pages can not be downloaded using basic
authentication, but you can capture the login page
through:
Add URL/Capture URL
This is not very simple to do, as you have to
temporary change your browser's proxy settings, but
the capture tool should give you a working URL (see in
the Documentation, interface)